Power limiters are commonly used in a variety of military and commercial microwave systems. The basic function of a power limiter is to protect sensitive electronics from RF powers above a predetermined critical value because some devices can be permanently damaged when subjected to an electrical field of a sufficient magnitude. An ideal RF limiter should have the following characteristics: EQU P.sub.out =P.sub.in, if P.sub.in .ltoreq.P.sub.max EQU P.sub.out =P.sub.max, if P.sub.in &gt;P.sub.max
wherein P.sub.in and P.sub.out are, respectively, the input signal power to the limiter and the output signal power from the limiter, and P.sub.max is the specific limiting power level of the power limiter. This implies that an ideal limiter would have zero "off" resistance when P.sub.in .ltoreq.P.sub.max, and would provide a proportional resistance as the device turns "on" such that the output signal is limited to P.sub.max when P.sub.in &gt;P.sub.max.
Standard power limiters are typically composed of single or multiple diodes (usually PIN diodes) either in a series or a shunt configuration to reflect and attenuate strong incident RF signals. When used in the series configuration, the diodes are biased off to reflect and attenuate the RF signal and when used in the shunt configuration the diodes are biased on to reflect the RF signal. In either of these configurations, the finite conductance characteristics of the PIN diode causes an undesired reflection and attenuation of the RF signal, that is, when the power limiter need not limit power. Therefore, these standard diode limiters always cause some insertion loss. Further, the inherent reactance of the conventional limiters limits the bandwidth or frequency range of operation. Examples of commercially available diode limiters can be found in various product catalogs, such as Triangle Microwave, 1986.
Accordingly, there is a need in the electronics industry to provide a power limiter with an increased bandwidth and a lower insertion loss. The present invention addresses such a need.